A filler, basically, usually added to the end of a sentance. Stereotypically said to be incessantly used by Canadians, just like everyone thinks all American teenaged girls with blonde hair say 'like' repeatedly, only 'eh' isn't so incredibly obnoxious IMO. Personally I've lived with canadians that say it, others that don't. Depends on the canuck. Plenty of Americans say it too. Can also be likened to the habit of adding 'then' to soften a sentance.

A word that is generalized as being used by Canadians. This is however just a generalization and although there may be some truth, not all Canadians will inject this at the end of a sentance. Made popular by Hollywood. The stereotype is made fun of in Canadian sitcoms.

Joe: Great show eh?

-Used here as some might use the word right. To make sure that the person you are talking to is paying attention.

a stereo-type made from americans that think we say it all the time. But when actually used, it used to make sure the listner comprehends or is even still listening, also a short way of asking after an opinion if the listner agrees with you or not.

BOB: "americans think we say "eh" all the time did you know that eh?"
SUE: Really? like how they think we live in igloo's and ride around on dog sleds aswell?